1. Technical Field
The present invention relates to a lifter rotation preventing structure.
2. Related Art
Japanese Patent Application Publication No. JP-A-2010-1884 discloses a sliding lifter which is reciprocably inserted into a sliding hole of a cylinder head. The sliding lifter includes a cylindrical body slidable in the sliding hole and an abutting portion connected to an inner periphery of the body. The body is formed with a pair of supports opposed to each other. A shaft has two ends fixed to the respective supports. A roller which is brought into sliding contact with a cam is rotatably supported on the shaft.
The abutting portion divides an interior of the body into a space at the side where the cam and the roller are located and another space located at the opposite side. An engaging member comprising a valve stem (in the case of a valve lifter) or a plunger (in the case of a pump lifter) is disposed in the space located at the aforementioned opposite side.
The engaging member is reciprocally moved according to the lifter reciprocated with rotation of the cam to open/close a valve or to pressure-feed fuel. The engaging member has an outer periphery to which a retainer is fixed. A coil spring is interposed between the retainer and a cylinder head to bias the lifter to the cam side.
The lifter body has an axial end having a part in which the supports are not formed. A rotation preventing protrusion is formed on the part of the axial end of the lifer body. The rotation preventing protrusion is inserted into a rotation preventing groove communicating with the sliding hole of the cylinder head, thereby preventing the lifter from rotation.
In the above-described conventional lifter, the rotation preventing protrusion is formed on the axial end of the body in consideration of workability and the like. Accordingly, there is a problem that an overall length of the body (a sliding length) would be limited by a position of the rotation preventing protrusion. For example, when the size of the lifter is reduced and a sufficient overall length of the body is not ensured, there is a possibility that the body would be tilted beyond an allowable range within a range of clearance in the sliding hole (cocking). Further, since the cylindrical shape of the body is impaired by the rotation preventing protrusion, a finish processing in which the body is fed in one direction in a through-feed manner is hard to carry out when an outer periphery of the body is ground, for example.